1. Field of the Invention
The present invention relates to flow-rate control valves.
This application is based on Japanese Patent Application No. 2008-177265, the content of which is incorporated herein by reference.
2. Description of Related Art
Conventionally, application of needle valves is known in the structures of valves for controlling the flow rates of liquids including chemical solutions.
Also known is a technique wherein a valve as mentioned above is provided with a stepping motor that drives and rotates a shaft body and also with a converting mechanism that converts the rotation of the shaft body into advancing/retracting movement of the shaft body to render the valve remotely controllable (see, e.g., Japanese Unexamined Utility Model Application, Publication No. Hei07-038843).
The converting mechanisms include one with an externally threaded shaft body and an internally threaded slider.
Valves using such a converting mechanism require an increased number of components as well as an increased man-hours for assembly of the valves, which not only leads to increased manufacturing costs of the valves but also to impairment of ease of maintenance.